The present invention relates generally to exhaust nozzles, and more particularly to nozzles for use with exhaust systems that evacuate fumes or otherwise draw undesirable air from within a building or enclosure.
There are many different types of exhaust systems for buildings and enclosed spaces. In areas such as laboratories and kitchens, fumes are often produced that have an unpleasant odor or are otherwise undesirable. It is common to outfit such environments with exhaust systems that draw the fumes from the building and dispel them through an exhaust port that is typically located on an external wall or roof of the building.
Furthermore, it is often desirable to expel the air a distance from the exterior of the building to avoid introducing it into the environment surrounding the building. Many conventional exhaust systems employ tall exhaust towers or stacks so that the air exits the building well above ground level. However, these exhaust stacks are expensive to construct and maintain and are generally considered unsightly.
Exhaust systems have been developed that use high velocity fans to force the air away from the building and surrounding area without the need for towers or stacks. Also, systems have been developed that combine the forced air exhaust systems with systems that mix the undesirable air with fresh air to dilute the concentration of the undesirable air before it is exhausted from the building at a high velocity. Such exhaust systems are commercially available from Greenheck Fan Corporation of Wisconsin under the Vektor model name. By diluting the undesirable air before release into the surrounding environment, these systems reduce the amount of separation desired between the release point and the surrounding environment. The air is thus forced to a desirable distance from the building and surrounding environment by fan power without the need for unsightly towers or stacks and the associated costs.
While these “stack-less” exhaust systems are desirable, they typically have associated maintenance costs and may not be suitable for a given application without significant adaptation for the particular performance specifications of the given application. For example, in some circumstances, a particular fan arrangement, that is, motor size, blade configuration, and/or nozzle configuration, may not achieve and sustain flow characteristics to achieve the plume height and flow volume necessary to exhaust the air a sufficient distance from the building and surrounding environment.
Drive motor sizing and fan blade size, quantity, and configuration affect the performance and efficiency of the exhaust system. The configuration of the outlet nozzle is also very important, as is the configuration of the windband that is placed about the nozzle to help entrain ambient air with the exhaust air exiting the nozzle. While many conventional windbands are open-ended annular structures that vary primarily by entry and exit diameter, the size and shape of the outlet nozzle can vary significantly and thus is one of the most important elements to consider when designing the exhaust system.
One example of an existing exhaust nozzle is described in U.S. Pat. No. 6,676,503. This patent discloses one exhaust nozzle configuration having an outlet defined by curved, convoluted outer walls that taper inwardly from an inlet side of the nozzle toward the outlet. The patent discloses outlets taking generally rounded X-, Y-, and I-shaped configurations, all of which are defined by inwardly tapering outer walls. A drawback with the disclosed nozzle is that the air exiting the nozzle moves in a generally inward direction toward the vertical centerline of the windband above the nozzle due to the inward taper of the nozzle walls. This does not optimally entrain ambient air with the building exhaust air, possibly because the periphery of the exiting air is not sufficiently turbulent or because the area of the flow path is not large enough. In any event, the result is less dilution of the undesirable air and a lower plume height due to lesser air mass passing through the windband.
As such, it would be desirable for an exhaust system to have an improved nozzle configuration that betters air expulsion.